Such a safety connection is known from U.S. Pat. No. 5,957,612. In this patent, a curtain rail is described which is suspended from, for instance, a ceiling via a number of safety connections. With a normal load on each safety connection, at least a load resulting from the weight of the suspended rail and a curtain suspended therefrom, the curtain rail is retained by the safety connections and coupled to the ceiling. However, when the safety connections are loaded abnormally, for instance when a person tries to end his life by hanging himself from the rail, the safety connections disconnect from the rail. As a result, the rail can be prevented from being used as an auxiliary means in suicide. A curtain rail system provided with such safety connection is, for instance, used in hospitals or psychiatric institutions.
Each safety connection known from the referred-to US patent comprises a lower and an upper outside tube, the lower tube being provided at an extremity with a plug extending in a tube socket of the upper tube. The tube socket and plug are detachably coupled to each other by a ring, provided between them in a channel of one of the elements, which ring is manufactured from elastic material such as, for instance, rubber. This elastic ring ensures that the tube socket and the plug disconnect under the influence of a tensile force equal to or greater than a particular threshold load. With a normal load which is below the threshold load mentioned, the tube socket and the plug are held together by the ring.
A disadvantage of the known safety connection is that the value of the threshold load mentioned is variable within a relatively large range of forces. As a result, it is uncertain whether the connection will actually disconnect at an abnormal loading of the safety connection. Variation of the threshold load can, firstly, be caused in that the elastic rings, over time, loose elasticity. Additionally, a part of an elastic ring can become jammed between the first and the second retaining element when these retaining elements and the ring are coupled to or uncoupled from each other, which hampers or even completely prevents uncoupling of the safety connection. Moreover, through such jamming, the elastic ring can be damaged.
Further, the known safety connection is particularly disadvantageous with respect to the relatively great diameter of the elastic ring mentioned. This great diameter is necessary, so that the ring can apply sufficiently great forces to the socket and the plug for holding the socket and plug together at normal load. Due to this necessarily great ring diameter, the safety connection can only be provided with an outer tube having a relatively great diameter, which is undesired from an aesthetic viewpoint.
Further, it is difficult to properly arrange each elastic ring in the channel of one of the retaining elements designed for reception of that ring, because the channel is not easily accessible from an environment. Additionally, the known safety connection consists of relatively many parts, which renders this connection relatively expensive.
Another disadvantage of the known safety connection is that the lower tube of each safety connection comes down with the rail after disconnection of the safety connections.